During chemical vapor deposition (CVD) of silicon oxide and other layers onto the surface of a substrate, the deposition gases released inside the processing chamber may cause unwanted deposition on areas such as the walls of the processing chamber. Unless removed, this unwanted deposition is a source of defects, e.g. particles, that may interfere with subsequent processing and adversely affect wafer yield.
To avoid such problems, the inside surface of the chamber is regularly cleaned to remove the unwanted deposition material from the chamber walls and similar areas of the processing chamber. This procedure may be performed as a standard chamber dry clean operation where an etchant gas is used to remove (etch) the deposited material from the chamber wall and other areas. During the dry clean operation, the chamber interior is exposed to a plasma from the etchant gas so that the etchant gas reacts with and removes the deposited material from the chamber walls. Such cleaning procedures may be performed between deposition steps for every wafer or every n wafers.
However, typical cleaning procedures have inherent setbacks. CVD chambers are typically equipped with a remote plasma source (RPS) to enable a radical based clean after chemical vapor deposition. In some systems, an RPS can also be a source for radicals that participate in film formation itself. The lifetime of the RPS unit is governed by the integrity of an internal surface layer. During a typical RPS/chamber cleaning process, internal surfaces of the RPS/chamber can undergo thermal shock due to the high temperatures (and large temperature variations) of a typical cleaning process. Thermal shock of an internal surface leads to crazing and flaking of one or more of the internal surfaces. Flaking of internal surfaces of an RPS/chamber results in defects present on other internal surfaces of an RPS/chamber and/or a substrate within the chamber. Defects include fluorine-containing aluminum (Al—F), fluorine-containing aluminum oxide (Al—O—F), hydrogen-containing aluminum (Al—H), and hydrogen-containing aluminum oxide (Al—O—H). Crazing and flaking also cause severe plasma arcing in the RPS and RPS block. Therefore, there is a need in the art for improved RPS/chamber cleaning processes that reduce the occurrence of thermal shock in an RPS/chamber.